1. Field of the Invention
The present invention relates to a freeze-drying apparatus which is effective for all fields in which freeze-drying has heretofore been used, for example, a food field of vegetables, fishes and shellfishes, fruits and processed foodstuffs, a pharmaceutical field of medicines and the like, and a cosmetic field and which can efficiently freeze and dry various objects to be dried in a short time.
2. Background Art
In conventional freeze-drying, to heat objects to be dried, heaters have usually been arranged for individual containers in which the objects to be dried are mounted, and the containers in which the objects to be dried are mounted have usually individually and directly been heated.
To arrange the heaters for the above individual containers has been a main cause for increase of a price of a freeze-drying apparatus. The present inventor has investigated a heating technology by far infrared rays in a reduced pressure tank over a long period of time, has invented a heating apparatus to containers in which objects to be dried are mounted, by far infrared rays under a reduced pressure and has filed an application for the invention.
In the conventional freeze-drying, heating to containers by radiant heat has not usually been effective under a reduced pressure, and hence there is usually used a method of directly applying heaters to the individual containers mounted on respective stages, to directly heat the containers, thereby causing sublimation in objects to be dried, by heat conduction. In a conventional freeze-drying apparatus, the heaters have to be prepared for the individual containers of the objects to be dried, and the very complicated expensive apparatus is forced to be formed. Moreover, only bottom surfaces of the containers of the objects to be dried are basically heated, and hence as a drying time, a very long time of, for example, 24 hours or 36 hours is required. Furthermore, since the objects to be dried are heated only from the bottom surfaces of the containers, a thickness of each of the objects to be dried is limited to about 7 mm at maximum, which has imposed a limit on product development.
As a conventional freeze-drying method of foods, there is disclosed a freeze-drying method characterized by freezing a fish-paste product containing ground fish meat, setting a pressure at drying to 0.6 to 0.65 Torr for the fish-paste product, performing first sublimation of drying the product in an environment at 35 to 45° C. for 1.5 to 2.5 hours, performing second sublimation of drying the product in an environment at 70 to 80° C. for 14 to 16 hours, and then performing third sublimation of drying the product in an environment at 45 to 55° C. for 23 to 25 hours (Jpn. Pat. Appln. Publication No. 2007-167014).